The present invention relates to a semiconductor device and to a method for manufacturing a semiconductor device, and relates in particular to a method for etching used in manufacturing a semiconductor device.
There are two basic principles for manufacturing semiconductor devices, such as micro-electromechanical systems (MEMS). The first available principle for manufacturing semiconductor devices is known as bulkmicromechanic (BMM). According to the bulkmicromechanic principle, a wafer substrate is provided, which may be a monocrystalline silicon substrate, and the necessary structures are etched into this wafer substrate. Thus, for example, when manufacturing an oscillator for an acceleration sensor, the self-supporting structure of the oscillator is formed into the wafer substrate.
The second basic principle for manufacturing semiconductor devices, such as micro-electromechanical systems, is known as surface-micromachining (SMM). In this case, the microstructures are manufactured by using structural and sacrificial films or layers, i.e., thin-film microstructures are fabricated by the selective removal of a sacrificial film. A polycrystalline silicon (poly-Si) may be deposited by low-pressure chemical vapor deposition (LPCVD) on a substrate, and silicon dioxide (SiO2) may typically be used for the sacrificial layer. Hydrofluoric acid (HF) may be used as a selective release etchant in poly-Si micromachining. In surface-micromachining, the substrate or wafer is essentially used as a carrier for the microstructures erected on the surface of the substrate.
In many cases a co-fabrication of surface-microstructures and microelectronic circuits is desirable from the perspectives of system performance and manufacturing costs. In this respect, it is highly desirable if the micro-electromechanical systems can be manufactured after the completion of integrated circuits comprising electronic circuits on or in the substrate. These electronic circuits may include a metallization such as, e.g., an aluminum (Al) metallization. Due to the use of hydrofluoric acid (HF) for etching the poly-Si sacrificial layer, integrated circuits that include electronic circuits may have to be covered in order to protect them from the HF etchant which would damage the integrated circuits already present on the substrate.
According to an example embodiment of the present invention, a method for manufacturing a semiconductor device includes the following steps: providing a substrate; depositing a first monocrystalline layer which is a sacrificial layer on the substrate; depositing a second monocrystalline layer which is a function layer on the first monocrystalline layer; and etching at least part of the first monocrystalline layer. The use of the first and second monocrystalline layers in accordance with this method may allow for performing a back-end etching of the sacrificial layer with an etchant, such as, e.g., H2O2, which may not be harmful to a metallization of an integrated circuit on the substrate, and therefore may allow for the integration of integrated circuits such as aluminum circuits, sensors, control circuitry, other elements, etc., on and/or in the substrate.
In another example embodiment of the present invention, SixGey may used for the first monocrystalline layer, which may allow for the integration of the foregoing method in existing processes for manufacturing semiconductor devices since SixGey does not have a contaminating effect. Thus, the first monocrystalline layer may be applied at a very early stage in the manufacturing process of the semiconductor device and may not have a negative influence on the temperature-budget of an existing process for manufacturing the semiconductor device. Also, the use of the monocrystalline sacrificial layer in surface-micromachining may allow for a monocrystalline function layer. The function layer may include a layer of the semiconductor device in which, by which and/or on which the function of the semiconductor device is effected.
These and other advantages and features of the present invention will become readily apparent to those of ordinary skill in the art after reading the following detailed description of exemplary embodiments of the present invention and studying the accompanying drawings.